This invention relates to a fuel system for use in an internal combustion engine for directly injecting high-pressure fuel into engine cylinders.
Fuel systems have been proposed which employ high-pressure fuel injectors for injecting directly into engine combustion chambers vehicular gasoline fuel pressurized to a high pressure level. In such fuel systems, a motor-driven, low-pressure pump pressurizes a source of fuel and delivers the pressurized fuel to an engine-driven, high-pressure pump which, in turn, communicates with the high-pressure fuel injectors. The engine-driven pump operates at low speeds and pressurize the fuel to an insufficient pressure level when the engine is being cranked. In order to provide a compensation for this problem, it is the conventional practice to place, upstream of the engine-driven pump, a motor-driven, high-pressure pump which is actuated to compensate for the lack of fuel pressure to the injectors when the engine is being cranked. However, such motor-driven, high-pressure pump is expensive and heavy and requires a large volume of space for equipment.
The present invention provides an improved fuel system of the type dirctly injecting fuel into engine combustion chambers which can supply fuel in sufficient amounts over the full range of engine operation without the requirement for any expensive, heavy and space consuming, motor-driven, high-pressurem pump.